JP6964946B2 - Control device for continuously variable transmission - Google Patents

Description

The present invention relates to a control device for a continuously variable transmission.

A belt-type CVT (Continuously Variable Transmission) is widely known as a transmission mounted on a vehicle.

The belt type CVT has a configuration in which an endless belt is wound around a primary pulley on the input side and a secondary pulley on the output side. When power from the engine is input to the primary pulley, the frictional force between the primary pulley and the belt transmits power from the primary pulley to the belt, and the frictional force between the secondary pulley and the belt causes the belt to secondary. Power is transmitted to the pulley.

Both the primary pulley and the secondary pulley include a fixed sheave and a movable sheave that is arranged so as to face the fixed sheave with a belt sandwiched between them and is movable in the opposite direction. The hydraulic pressure supplied to each movable sheave of the primary pulley and the secondary pulley moves each movable sheave, changes the groove width of each of the primary pulley and the secondary pulley, and changes the winding diameter of the belt with respect to the primary pulley and the secondary pulley. As a result, the gear ratio of the CVT changes continuously and steplessly.

In gear ratio control, for example, a gear ratio target is set, and the belt transmission torque capacity required to prevent belt slippage is based on the set target gear ratio and the input torque input to the primary pulley. Is required. In addition, the thrust ratio is set according to the target gear ratio and the input torque. The thrust ratio is the ratio of the thrust of the primary pulley to the thrust of the secondary pulley. After that, the command values of the primary thrust, which is the thrust of the primary pulley, and the secondary thrust, which is the thrust of the secondary pulley, are obtained from the belt transmission torque capacity and the thrust ratio. The command values of the primary pressure, which is the hydraulic pressure supplied to the movable sheave of the pulley, and the secondary pressure, which is the hydraulic pressure supplied to the movable sheave of the secondary pulley, are set. Then, based on each command value of the primary pressure and the secondary pressure, the valve that supplies the oil pressure to each movable sheave of the primary pulley and the secondary pulley is controlled.

In a vehicle that uses a mechanical oil pump driven by the power of the engine as the source of oil pressure, the oil pump does not generate oil pressure while the engine is stopped, so the line pressure that is the main pressure of the primary pressure and secondary pressure is descend. When the engine is started, the oil pump operates and the line pressure rises due to the oil pressure generated by the oil pump. If the primary pressure rises as the line pressure rises, the lowest gear ratio (maximum pulley ratio) cannot be maintained. Therefore, it has been proposed to set the command value of the primary pressure to 0 MPa at the time of starting the engine to secure the lowest gear ratio and secure the startability of the vehicle.

Japanese Patent No. 6106287

However, since the primary pressure is maintained at the minimum pressure, if the input torque suddenly increases when the vehicle starts, the rise of the primary pressure is delayed in response to the increase, and belt slippage may occur due to insufficient pinching pressure. There is.

An object of the present invention is to provide a continuously variable transmission control device capable of suppressing belt slippage when a vehicle starts following the start of an engine.

In order to achieve the above object, in the control device for the stepless transmission according to the present invention, an endless belt is wound around the engine, the primary pulley and the secondary pulley, and the hydraulic pressure supplied to the primary pulley and the secondary pulley is supplied. As a result, the thrust ratio between the primary thrust, which is the thrust of the primary pulley, and the secondary thrust, which is the thrust of the secondary pulley, changes, the pulley ratio between the primary pulley and the secondary pulley changes, and the power from the engine is changed by the pulley ratio. A control device used in a vehicle equipped with a stepless transmission to control the stepless transmission, and sets a thrust ratio at which the pulley ratio is maintained at a predetermined maximum pulley ratio when the engine is started. From the thrust ratio setting means and the thrust ratio set by the thrust ratio setting means, each command value of the primary thrust and the secondary thrust is set, and the hydraulic pressure supplied to the primary pulley and the secondary pulley is set based on each command value. It includes a feed forward control means for controlling feed forward.

According to this configuration, when the engine is started, a thrust ratio that keeps the pulley ratio at a predetermined maximum pulley ratio is set. Then, each command value of the primary thrust and the secondary thrust is set from the set thrust ratio, and the oil pressure supplied to the primary pulley and the secondary pulley is feedforward controlled based on each command value. As a result, when the engine is started, the primary pressure, which is the oil supply to the primary pulley, is boosted to a pressure larger than 0 MPa while ensuring the maximum pulley ratio. Therefore, it is possible to suppress the occurrence of belt slippage when the vehicle starts following the start of the engine, and it is possible to secure the maximum pulley ratio when the vehicle starts.

The thrust ratio setting means may set the thrust ratio to a value smaller than the maximum value of the thrust ratio at which the pulley ratio is held at the maximum pulley ratio. As a result, the maximum pulley ratio can be satisfactorily secured when the vehicle starts.

The control device provides a correction means for correcting at least one of the primary thrust and secondary thrust command values when a situation occurs in which the actual thrust ratio exceeds the maximum value of the thrust ratio held at the maximum pulley ratio. The configuration may further include. As a result, the maximum pulley ratio can be more satisfactorily secured when the vehicle starts.

According to the present invention, it is possible to suppress belt slippage when the vehicle starts following the start of the engine.

It is a figure which shows the structure of the main part of the vehicle which used the ECU which concerns on one Embodiment of this invention. It is a flowchart which shows the content of the pulley ratio control at the time of starting an engine. It is a figure which shows the relationship between a pulley ratio and a thrust ratio. It is a figure which shows the time change of the engine speed, the primary pressure and the secondary pressure at the time of starting an engine. It is a figure which shows the relationship between the primary thrust and the secondary thrust.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Main part composition of the vehicle>
FIG. 1 is a diagram showing a configuration of a main part of a vehicle 1 in which the ECU 41 according to the embodiment of the present invention is used.

The vehicle 1 is equipped with an engine 2 and a belt-type continuously variable transmission (CVT) 3.

The continuously variable transmission 3 has a primary shaft 11, a secondary shaft 12 provided parallel to the primary shaft 11, a primary pulley 13 supported by the primary shaft 11 so as to be relatively non-rotatable, and a secondary shaft 12 so as to be relatively non-rotatable. A supported secondary pulley 14 and a belt 15 wound around the primary pulley 13 and the secondary pulley 14 are provided.

For example, the power of the engine 2 is input to the primary shaft 11 via a torque converter. The power input to the primary shaft 11 is transmitted from the primary pulley 13 to the belt 15 by the frictional force between the primary pulley 13 and the belt 15, and is transmitted to the belt 15 by the frictional force between the secondary pulley 14 and the belt 15. Is transmitted to the secondary pulley 14. The power transmitted to the secondary pulley 14 is transmitted from the secondary shaft 12 to the differential gear, and is transmitted from the differential gear to the left and right drive wheels via the left and right drive shafts, respectively.

The primary pulley 13 is a movable sheave that is arranged so as to face the fixed sheave 21 fixed to the primary shaft 11 and the fixed sheave 21 with the belt 15 interposed therebetween, and is supported by the primary shaft 11 so as to be movable in the axial direction and not to rotate relative to each other. It has 22 and. A piston 23 fixed to the primary shaft 11 is provided on the side opposite to the fixed sheave 21 with respect to the movable sheave 22, and a hydraulic chamber 24 is formed between the movable sheave 22 and the piston 23.

The secondary pulley 14 is arranged to face the fixed sheave 25 fixed to the secondary shaft 12 with the belt 15 sandwiched between the fixed sheave 25, and is supported by the secondary shaft 12 so as to be movable in the axial direction and non-relatively rotatable. It is equipped with a movable sheave 26. A piston 27 fixed to the secondary shaft 12 is provided on the side opposite to the fixed sheave 25 with respect to the movable sheave 26, and a hydraulic chamber 28 is formed between the movable sheave 26 and the piston 27.

The hydraulic pressure supplied to the hydraulic chamber 24 of the primary pulley 13, that is, the primary pressure acting on the movable sheave 22 of the primary pulley 13, causes the movable sheave 22 of the primary pulley 13 to move in the axial direction of the primary shaft 11 to move with the fixed sheave 21. The groove width, which is the distance from the movable sheave 22, changes continuously. Further, the movable sheave 26 of the secondary pulley 14 moves in the axial direction of the secondary shaft 12 due to the hydraulic pressure supplied to the hydraulic chamber 28 of the secondary pulley 14, that is, the secondary pressure acting on the movable sheave 26 of the secondary pulley 14, and the fixed sheave. The groove width, which is the distance between the 25 and the movable sheave 26, changes continuously. By continuously changing the groove widths of the primary pulley 13 and the secondary pulley 14, the winding diameter of the belt 15 with respect to the primary pulley 13 and the secondary pulley 14 is continuously changed, and the primary pulley 13 and the secondary pulley 14 are brought into contact with each other. The pulley ratio can be changed steplessly and continuously.

The continuously variable transmission 3 is provided with a hydraulic circuit 31 for supplying oil to each part of the continuously variable transmission 3. The hydraulic circuit 31 includes a valve for supplying a primary pressure and a secondary pressure to the primary pulley 13 and the secondary pulley 14, respectively.

Further, the vehicle 1 is provided with an ECU (Electronic Control Unit) 41 having a configuration including a microcomputer (microcontroller unit). Although only one ECU 41 is shown in FIG. 1, the vehicle 1 is equipped with a plurality of ECUs having the same configuration as the ECU 41 in order to control each part. A plurality of ECUs including the ECU 41 are connected so as to be capable of bidirectional communication by a CAN (Controller Area Network) communication protocol.

The ECU 41 controls various valves included in the hydraulic circuit 31 for pulley ratio control for controlling the pulley ratio of the continuously variable transmission 3. A sensor required for control, for example, a hydraulic sensor that detects a primary pressure and a secondary pressure, respectively, is connected to the ECU 41.

<Pulley ratio control>
FIG. 2 is a flowchart showing the contents of pulley ratio control at the time of starting the engine 2. FIG. 3 is a diagram showing the relationship between the pulley ratio and the thrust ratio. FIG. 4 is a diagram showing changes over time in engine speed, primary pressure, and secondary pressure when the engine is started. FIG. 5 is a diagram showing the relationship between the primary thrust and the secondary thrust.

In the pulley ratio control by the ECU 41, as shown in FIG. 2, first, the required belt torque capacity, which is the belt transmission torque capacity required to prevent the belt slippage in the continuously variable transmission 3, is obtained (step S1). The required belt torque capacity can be obtained from the target pulley ratio, which is the target of the pulley ratios of the primary pulley 13 and the secondary pulley 14, and the input torque input to the primary shaft 11.

Further, the thrust ratio according to the target pulley ratio and the input torque is calculated (step S2). The thrust ratio is the ratio of the primary thrust, which is the thrust of the primary pulley 13, to the secondary thrust, which is the thrust of the secondary pulley 14. As shown in FIG. 3, the larger the pulley ratio, the smaller the thrust ratio, and in the range where the thrust ratio is a certain value Ra or less, the maximum pulley ratio, that is, the maximum Lo value is taken. When the engine 2 is started, the target pulley ratio is set to the maximum Lo value, and the thrust ratio is set to a value equal to or less than a constant value Ra.

Next, each command value of the primary thrust and the secondary thrust according to the required belt torque capacity and the thrust ratio is calculated (step S3). When the pulley ratio takes the maximum Lo value, the primary thrust (primary thrust) and secondary thrust (secondary thrust) required to prevent belt slippage can be calculated according to the following equation.

Primary required thrust = Secondary required thrust = Input torque x cosθ / (2 x belt friction coefficient x belt winding diameter)

Here, θ is the gradient of the pulley cone surface which is the contact surface of the primary pulley 13 with the belt 15, and the belt winding diameter is the winding diameter of the belt 15 with respect to the primary pulley 13.

Therefore, the command value of the primary thrust is set to the primary required thrust, and the command value of the secondary thrust is set to the value obtained by dividing the secondary required thrust by the thrust ratio.

Then, it is determined whether or not the feedback control is not possible at the time of starting the engine 2 (at the time of starting the engine) (step S4). Since the accuracy of detecting the rotation speed of each shaft is insufficient, the calculation accuracy of the actual pulley ratio is also insufficient, and as shown in FIG. 4, feedback control in the pulley ratio control is impossible. After the engine 2 is started, when the rotation speed of each shaft increases and the primary pressure and the secondary pressure stabilize, feedback control in the pulley ratio control becomes possible.

When the feedback control is disabled (YES in step S4), the command pressures of the primary pressure and the secondary pressure are set from the command values of the primary thrust and the secondary thrust. Then, feedforward control of the primary pressure and the secondary pressure is executed based on the respective command values of the primary pressure and the secondary pressure (step S5).

Then the actual primary and secondary thrusts are calculated. The actual primary thrust is calculated by multiplying, for example, the actual pressure of the primary pressure detected by the pressure sensor and the pressure receiving area of the movable sheave 22 of the primary pulley 13. The actual secondary thrust is calculated by multiplying, for example, the actual pressure of the secondary pressure detected by the pressure sensor and the pressure receiving area of the movable sheave 26 of the secondary pulley 14. Then, the actual thrust ratio is obtained by dividing the actual primary thrust by the actual secondary thrust, and this actual thrust ratio is the maximum value of the thrust ratio that can secure the pulley ratio of the maximum Lo, that is, a constant value. Whether or not it is larger than Ra is determined (step S6).

For example, after the engine 2 is started, the oil generated by the oil pump driven by the power of the engine 2 may rise sharply, and the line pressure, which is the main pressure of the primary pressure, may rise sharply accordingly. As a result, when an overshoot occurs in which the actual pressure of the primary pressure exceeds the command pressure, the pressure receiving area of the movable sheave 22 of the primary pulley 13 is generally larger than the pressure receiving area of the movable sheave 26 of the secondary pulley 14, so that the primary The thrust becomes excessive, and the actual thrust ratio becomes larger than the constant value Ra.

When the actual thrust ratio is larger than the constant value Ra (YES in step S6), the command values of the primary pressure and the secondary pressure are corrected based on the actual pressures of the primary pressure and the secondary pressure (step S7). For example, when the target pulley ratio and the thrust ratio according to the input torque are constant values Ra = 0.5, the command value of the secondary thrust is increased as shown in FIG. 5, and the broken line and the solid line are shown in FIG. As shown by, the command value of the secondary pressure is raised. As a result, the maximum Lo pulley ratio is secured.

On the other hand, in a state where feedback control is possible (NO in step S4), feedback control is performed so that the actual pulley ratio matches the target pulley ratio (step S8).

<Effect>
As described above, when the engine 2 is started, the thrust ratio that can hold the pulley ratio at the maximum Lo pulley ratio, that is, the maximum pulley ratio is set. Then, each command value of the primary thrust and the secondary thrust is set from the set thrust ratio, and the oil pressure supplied to the primary pulley 13 and the secondary pulley 14 is feedforward controlled based on each command value. As a result, when the engine 2 is started, the primary pressure is boosted to a pressure larger than 0 MPa while ensuring the maximum pulley ratio. Therefore, it is possible to suppress the occurrence of belt slippage when the vehicle 1 starts following the start of the engine 2, and it is possible to secure the maximum pulley ratio when the vehicle 1 starts.

Further, when a situation occurs in which the actual thrust ratio exceeds the maximum value Ra of the thrust ratio held by the maximum pulley ratio, the command value of the secondary thrust is corrected and the secondary pressure is increased. As a result, the maximum pulley ratio can be more satisfactorily secured when the vehicle 1 starts.

<Modification example>
Although one embodiment of the present invention has been described above, the present invention can also be implemented in other embodiments.

For example, in the above-described embodiment, when a situation occurs in which the actual thrust ratio exceeds the maximum value Ra of the thrust ratio held at the maximum pulley ratio, the command value of the secondary thrust is corrected and the secondary pressure is increased. It was said that it could be raised. Not limited to this, when the actual thrust ratio exceeds the maximum value Ra of the thrust ratio held at the maximum pulley ratio, the command value of the primary thrust is corrected within the range where belt slip does not occur. The primary pressure may be lowered.

Further, although the vehicle 1 equipped with the belt type continuously variable transmission 3 is taken up, the control device according to the present invention is used not only for such a vehicle 1 but also for a vehicle equipped with a power split type continuously variable transmission 3. You can also do it. The power split type continuously variable transmission is provided with, for example, a continuously variable transmission mechanism for steplessly changing the power by changing the pulley ratio, and the power is divided and transmitted between the input shaft and the output shaft by two paths. It is a possible transmission.

In addition, various design changes can be made to the above-mentioned configuration within the scope of the matters described in the claims.

1: Vehicle 2: Engine 3: Continuously variable transmission 13: Primary pulley 14: Secondary pulley 15: Belt 41: ECU (control device, thrust ratio setting means, feedforward control means, correction means)

Claims (3)

A continuously variable belt is wound around the engine, the primary pulley and the secondary pulley, and the thrust of the primary pulley and the thrust of the secondary pulley are generated by the hydraulic pressure supplied to the primary pulley and the secondary pulley. It is used in vehicles equipped with a continuously variable transmission that changes the thrust ratio to the secondary thrust, changes the pulley ratio between the primary pulley and the secondary pulley, and shifts the power from the engine by the pulley ratio. , A control device that controls the continuously variable transmission.
A feedback control means that feedback-controls the hydraulic pressure supplied to the primary pulley and the secondary pulley so that the actual pulley ratio matches the target pulley ratio, which is the target of the pulley ratio.
A thrust ratio setting means for setting a thrust ratio at which the pulley ratio is maintained at a predetermined maximum pulley ratio when the engine is started.
From the thrust ratio set by the thrust ratio setting means, each command value of the primary thrust and the secondary thrust is set, and based on the respective command values, the hydraulic pressure supplied to the primary pulley and the secondary pulley is feedforward controlled. look including a feed-forward control means for,
Whether or not the feedback control is possible at the time of starting the engine is determined, the feedforward control is performed by the feedforward control means when the feedback control is not possible, and the feedback control means is performed when the feedback control is possible. A control device that performs the feedback control according to the above. The control device according to claim 1, wherein the thrust ratio setting means sets the thrust ratio to a value smaller than the maximum value of the thrust ratio held at the maximum pulley ratio. Further including a correction means for correcting at least one of the command values of the primary thrust and the secondary thrust when a situation occurs in which the actual thrust ratio exceeds the maximum value of the thrust ratio held by the maximum pulley ratio. The control device according to claim 1 or 2.

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